Sponge rubber and method of making the same



UNITED STATES PATENT OFFICE SPONGE RUBBER AND METHOD or MAKING THE SAMEGlen S. Hiers, Cynwyd, Pa., assignor to Collins & Aikman Corporation,Philadelphia, Pa., a corporation of Delaware No Drawing. ApplicationJuly 31, 1933, Serial No. 683,102

9 Claims. (CI. 18-50) My invention is an improved sponge rubbersolutions; the negative action of iodine solution which is free fromacid or acid'compounds, and on solutions thereof; the stringyprecipitate reamethod of making sponge rubber from a frothed sultingfrom the addition of neutral ferric chloor spongy aqueous rubberdispersion without acid ride to solutions thereof; and the precipitaterecoagulation, and preferably by the direct action sulting from theaddition of tannic acid to soluof heat which liberates the cell forminggas, coagtions thereof. From a consideration of their ash, ulates therubber in cellular form, drives ofi the their ready conversion to anuronic acid, the water, and cures the rubber. By my improvenature oftheir hydrolysis products and oxidation ments I am able to form spongerubber while to mu'cic acid, they have been found to contain 10maintaining the rubber globules in an alkaline small quantities of acidpolysaccharids and prob- 10 medium and to more accurately control thepoably belong to the class of polysaccharids known rosity of thefinished product. as hemicelluloses.

In accordance with my invention, I add to latex As an illustration ofthe pra of y invena gum or gums coagulable by the addition of an tion,there may be added toa latex compound conalkali thereto to form a gel orcoagulum of desired t ming. s y, of r r l d nd a l v 15 stiffness havinguncoagulated rubber globules discanizers and anti-oxidantaa 1% ofdispersion persed therein. Such gel or coagulum may be of locust-kernelgum to a sufficient extent that irothed or rendered spongy in anysuitable manthere is present 0.56% of the solid locust kernel ner, butpreferably by the evolution of gas from gum on the basis of the rubbersolid content a suitable non-acid chemical dispersed through To this maybe added suitable gas forming in- 20 the mixture of gum and latex beforethe gelling gredients, such, for instance, as ammonium carthereof. ,Suchevolution of gases is preferably bonate, ammonium chloride or ammoniumsuleffected by the application to the gel of sufficient Dh in he form ofa dry powdered salt. Prefheat to decompose the chemicals, coagulate theerably the gas forming material consists of a dry rubber globules, driveoil the water contained in ammonium carbonate approximating to 60% 25the gel, and cure the rubber. by weight of the dry rubber solidscontent. The

To obtain a sponge rubber substantially free liquid may then be placedin suitable molds or from impurities it is advantageous to utilize aapplied to the back of fabrics and on the addicoagulable gum having avery high viscosity in tion of a borax solution a gel is immediately 30very dilute concentrations, and which gels very formed. The amount ofborax (dry base) may 30 rapidly in the presence of a small quantity ofadvantageously approximate in weight the the alkaline reagent. amount oflocust-kernel gum present.

I preferably utilize for addition to the latex Upon subjecting the gelto a temperature of minute quantities of certain vegetable gums gensay210 F., the salt is decomposed with liberaerally identified aspolysaccharids which in solution of the gas which is entrapped by thegel and tion are caused to gel by the addition of an alkaforms a frothor sponge. The continued appliline salt of boric acid, such as borax,and which cation of the heat also causes the coagulation are compatiblewith and do not tend to coagulate of the rubber globules around the gascells. rubber. These gums are preferably white, odor- Upon theevaporation of the water contained in less, tasteless powders derivedfrom vegetable the gel, the rubber may be cured to a desired 40 gumshaving the characteristics of carob-seed de-' degree by the continuedapplication of a vulrivatives. Such gums are commonly known as canizingheat.

caroban, locust-kernel gum, locust bean gum, By using gum solutions andborax solutions of carob-seed gum, carob-bean gum, gum I-Ievo, gumsuitable concentrations, rubber containing jellies Gatto,gum Tragon,Jandagum, Lakoe gum, Lupoof varying consistencies and firmness may begum, Luposol, Rubigum, Tragarab, Tragasol, Galformed varying from gelsformed from very dilute agum, Emulsone, Kern, Koniaku, etc., and aresolutions containing 0.25% gum or less, which generally prepared fromthe fruit of the carob liquefy readily in the presence of heat, tojellies tree (Ceritoniw siliqua) or Conaphallus koniah. which arepractically unafiected when heated All of these gums may be identifiedprimarily by 100 C. and are practically heat irreversible gels. 50

the gelling action of borax on solutions thereof; Having described myinvention I claimand secondarily by the voluminous precipitate and 1.Asponge rubber formed from an aqueous gelling resulting from the additionof neutral lead rubber dispersion containing borax and a vegeacetatetosolutions thereof and gelling resulting table gum coagulable by saidborax, and, a cell.

from the addition of basic lead acetate to such forming agent. 55

2. In the preparation of sponge rubber the steps which consist in addingto aqueous rubber a vegetable gum jellifiable by borax, gelling thesolution formed by such gum and dispersion by adding borax, frothing thegel and coagulating the rubber.

3. In the preparation of sponge rubber, the steps which consist inmixing an aqueous dispersion of rubber with a vegetable gum derived fromthe fruit of the botanical group Ceritom'a silz'qua or Conaphalluskom'ah, gelling such mixture, frothing the gel, driving off the waterfrom the gel and coagulating the rubber globules therein by heat.

4. In the preparation of sponge rubber, the steps which consist inmixing with an aqueous dispersion of rubber a gel-forming gum derivedfrom the fruit of the botanical group Ceritom'a siliqua or Conaphalluskom'ah and a gas-forming ingredient, gelling said mixture, heating saidgel to evolve gas from said ingredient, driving off the water containedin said gel, and coagulating said rubber.

5. In the preparation of sponge rubber, the steps which consist inmixing with an aqueous rubber dispersion a solution of a vegetable gumhaving the characteristics of carob-seed deriva tives, gelling saidmixture by the addition of an alkaline salt of boric acid, and frothingand heating said gel.

6. In the preparation of sponge rubber, the steps which consist inadding to an aqueous rubber dispersion a vegetable gum gellifiable byborax, gelling such gum by adding borax, pufiing the mixture ofdispersion and gum, and removing the Water.

7. A rubber containing jelly consisting of borax and a solution of a gumderivative of the fruit of the botanical group Ceritonia sz'lz'qua orConaphallus kony'ah and. having rubber globules dispersed in the jelly.

8. The method of forming rubber containing jellies which consists inmixing together rubber and .a solution of gum formed from the fruit ofthe botanical group Ceritom'a silzqua or Conaphallus Icona'ah andgelling the mixture by the addition thereto of an alkaline salt of boricacid.

9. A sponge rubber formed from an aqueous rubber dispersion containingborax, and a vegetable gum coagulable by borax, and a blowing agent.

GLEN S. HIERS.

